Seymour, Polymers for Engineering Applications, ASM International (1987), Gowariker et al., Polymer Science, John Wiley & Sons Inc. (1986) and Barrett (Ed.), Dispersion Polymerization in Organic Media, John Wiley & Sons Inc. (1975) are recommended background reading material.
Polymer/polyol compositions suitable for use in producing polyurethane foams, elastomers and the like, and the polyurethanes, are commercial products. The two major types of these polyurethane foams are termed slabstock and molded. Slabstock foams are used in the carpet, furniture and bedding industries. Primary uses of slabstock foam are as carpet underlay and furniture padding. In the molded foam area, high resiliency (HR) molded foam is the foam type generally made. HR molded foams are used in the automotive industry for a breadth of applications ranging from molded seats to energy-absorbing padding and the like.
The basic patents relating to such polymer/polyol compositions are Stamberger Re. U.S. Pat. Nos. 28,715 (reissue of U.S. Pat. No. 3,383,351) and Re. 29,118 (reissue of U.S. Pat. No. 3,304,273). A stable dispersion of polymer particles in a polyol can be produced by polymerizing one or more ethylenically unsaturated monomer dissolved or dispersed in a polyol in the presence of a free radical catalyst. These polymer/polyol compositions produce polyurethane foams and elastomers having higher load-bearing capacities than those produced from unmodified polyols.
Initially, the primary polymer/polyol compositions accepted commercially used acrylonitrile in its manufacture. Many of these compositions possessed undesirably high viscosities for certain applications. More recently, acrylonitrile-styrene monomer mixtures have been used commercially to make the polymer component of polymer/polyols.
The expanding demand for polymer/polyols has highlighted several product needs and this has spawned additional advances in technology. For example, a market demand has evolved for "virtually" scorch-free slabstock foams, i.e., white foam products. Virtually scorch-free foams possessing satisfactory load-bearing and other foam properties, even at ever-decreasing densities (viz.--1.5 pounds per cubic foot or less), are available without substantial economic penalty.
Virtually scorch-free foams are achieved by using relatively high styrene contents (e.g., --about 65 to 70 percent styrene) in the acrylonitrilestyrene monomer mixture. In addition, such high styrene monomer mixtures are used broadly in the molded foam area.
Still, polymer/polyols derived from such high styrene monomer mixtures appear incapable of satisfying ever-increasing market needs, which include rigorous stability requirements and increased load-bearing characteristics. This is particularly prevalent in the slabstock area where many formulations require the use of "neat" polymer/polyols, i.e., polymer/polyol undeluted by conventional polyols. Though neat polymer/polyols are not usually employed in the molded foam area, there is a need for polymer/polyols which can impart higher load-bearing characteristics to such foams.
Polymer/polyols with increased load-bearing characteristics can be obtained by increasing their polymer or solid contents. Solid contents of 30 to 60 weight percent, or higher, are desired. Yet, the art has not been capable of increasing solid contents without reducing the stability of the polymer/polyol and undesirably increasing its viscosity.
Employment of high styrene monomer mixtures and high solid contents' polymer/polyols, by prior practices, generally resulted in undesirably high viscosity polymer/polyols. The viscosity of a polymer/polyol should be sufficiently low for ease of handling during its manufacture. In addition, the viscosity should facilitate transport, handling and, ultimately, adequate processability, in the employed foam processing equipment. Because of increased usage of sophisticated mixing systems, such as impingement systems, excessive viscosity of the polymer/polyol is becoming a significant problem in the molded area. The need for lower viscosity polymer/polyols is apparent to satisfy these increased demands in the art.
As indicated, polymer/polyol stability is a concern to makers of polyurethanes. Once, seediness or filterability, a measure of stability of polymer/polyols, was not a major issue in commercial practices. With advances in the state of the art of polyurethane production, polymer/polyol stability criteria were revised, especially in the molded foam area.
With commercial developments in sophisticated, high-speed and large-volume equipment and systems for handling, mixing and reacting polyurethane-forming ingredients have evolved the need for highly stable and low viscosity polymer/polyols. Polymer/polyols have certain minimum requirements for satisfactory processing in such sophisticated foam equipment. Typically, the prime requirement is that the polymer/polyols possess sufficiently small particles so that filters, pumps and the like do not become plugged or fouled in relatively short periods of time.
Though there have been advances in reduction in viscosity and increase in solids of polymer/polyols, there is a need for improvement in viscosity reduction and increase in solids content. Greater reductions in viscosity are needed to meet market demands and greater effective increases in solids content are also needed by the market. More importantly, there is a need for technology in polymer/polyol that maximizes viscosity reduction while also providing a viable mechanism to higher solids content.
Priest et al., U.S. Pat. No. 4,208,314 describe low viscosity polymer/polyols made from acrylonitrile-styrene monomer mixtures. These polymer/polyols are convertible to low density, water-blown polyurethane foams having reduced scorch, especially with relatively low acrylonitrile-to-styrene ratios. The Priest et al. patent also provides a process for making polymer/polyols with reduced particulates.
Enhanced stability of polymer/polyols is believed to be provided by the presence of a minor amount of a graft or addition copolymer formed in situ from growing polymer chains and polyol molecules. Some prior approaches incorporate small amounts of unsaturation into the polyol in addition to that inherently present in the polyoxyalkylene polyols typically used in forming polymer/polyols. This was done in the belief that improved stability will result due to an increased amount of an addition copolymer stabilizer expected to be formed. U.S. Pat. Nos. 3,652,639, 3,823,201, and 3,850,861, British Patent No. 1,126,025 and Japanese Patent Nos. 52-80919 and 48,101494 utilize this approach. This use of "stabilizer precursors," also termed a "macromer" that contains a particular level of reactive unsaturation, is based on the belief that during polymerization, in the preparation of the polymer/polyol, adequate amounts of stabilizer will be formed by the addition polymerization of the precursor stabilizer with a growing polymer chain.
The general concept of using stabilizer precursors in polymerization is discussed in Barrett (1975), supra. U.S. Pat. Nos. 4,454,255 and 4,458,038 illustrate this technique. The macromer in the '255 and '038 patents may be obtained by reacting a polyol with a compound having reactive ethylenic unsaturation such as, for example, maleic anhydride or fumaric acid. A further example of the use of this technique is U.S. Pat. No. 4,460,715. The reactive unsaturation in the '715 stabilizer is provided by an acrylate or methacrylate moiety.
Van Cleve et al., U.S. Pat. No. 4,242,249 disclose improved polymer/polyols prepared by utilizing certain preformed dispersants or stabilizers. These polymer/polyols provide stability satisfactory for commercial production, and use of one or more of the following: (1) higher amounts of styrene or other comonomer when acrylonitrile copolymer polymer/polyols are being prepared, (2) higher polymer contents or (3) the use of lower molecular weight polyols. The particular dispersant employed and the concentration utilized vary with respect to the monomer system used in preparing the polymer/polyols.
U.S. Pat. No. 4,550,194 prepares a polyol by reacting a conventional polyether polyol with an organic compound having ethylenic unsaturation and an anhydride group forming a half ester and subsequently reacting that product with alkylene oxide in the presence of calcium naphthenate or cobalt naphthenate. Example 51 of the patent uses pentaerythritol.
Simroth et al., U.S. Pat. No. 4,652,589, patented Mar. 24, 1987, describe stabilizer precursors for polymer/polyols. Stabilizer A is made by reacting a 34 hydroxyl number, 15 weight percent ethylene oxide capped polyoxyproxylene triol with maleic anhydride and subsequently with ethylene oxide. The stabilizer precursor has a hydroxyl number of 32, an unsaturation of 0.1 meq/gm, with the unsaturation being 30/70 maleate/fumarate. The retained unsaturation is 50 percent of the unsaturation provided by the maleic anhydride. Stabilizer B is made by reacting a 28 hydroxyl number sorbitol started polyol, containing 10% internal ethylene oxide, with maleic anhydride, and subsequently with propylene oxide. The precursor stabilizer has a hydroxyl number of 28 and an unsaturation of approximately 0.07 meq/g, with the unsaturation being of the fumarate type. The retained unsaturation is 70 percent of the unsaturation provided by the maleic anhydride.
European Patent Application 87114233.7, based on copending U.S. application Ser. No. 913,328, filed Sep. 30, 1986, is directed to stabilizers having four key features: (1) they are prepared from a starting polyol having a functionality greater than 4; (2) they have at least 60% retained unsaturation; (3) they have viscosities greater than 2000 centipoises at 25.degree. C.; and (4) the starting polyol is capped with ethylene oxide and/or the adduct formed between the starting polyol and the a reactive unsaturated compound is capped with ethylene oxide.
Other prior art of interest include Simroth et al., U.S. Pat. Nos. Re. 32,733, patented Aug. 16, 1988, Ramlow et al., 3,931,092, patented Jan. 6, 1976, Ramlow et al., 4,014,846, patented Mar. 29, 1977, Ramlow et al., 4,093,573, patented Jun. 6, 1978, Shah, 4,148,840, patented Apr. 10, 1979, Shook et al., 4,172,825, patented Oct. 30, 1979, Kozawa et al., 4,342,840, patented Aug. 3, 1982, Hoffman et al., 4,390,645, Jun. 28, 1983, Hoffman, 4,394,491, Jul. 19, 1983, Ramlow et al., 4,454,255, patented Jun. 12, 1984, Ramlow et al., 4,458,038, Jul. 3, 1984, and Hoffman, 4,745,153, patented May 17, 1988.
As used herein, the following terms shall have the following meanings:
"monomer"--the simple unpolymerized form of chemical compound having relatively low molecular weight, e.g., acrylonitrile, styrene, methyl methacrylate, and the like. PA0 "free radically polymerizable ethylenically unsaturated monomer"--a monomer containing ethylenic unsaturation (&gt;C.dbd.C&lt;) that is capable of undergoing free radically induced addition polymerization reactions. PA0 "stability"--the ability of a material to maintain a stable form such as the ability to stay in solution or in suspension. PA0 "polymer polyol"--Such compositions can be produced by polymerizing one or more ethylenically unsaturated monomers dissolved or dispersed in a polyol in the presence of a free radical catalyst to form a stable dispersion of polymer particles in the polyol. These polymer/polyol compositions have the valuable property of imparting to, for example, polyurethane foams and elastomers produced therefrom, higher load-bearing properties than are provided by the corresponding unmodified polyols. PA0 "viscosity"--in centistokes (cSt) measured at 25.degree. C. on a Cannon Fenske viscometer. PA0 "organic polyisocyanate"--organic compounds that contain at least two isocyanato groups and include the hydrocarbon diisocyanates (e.g., the alkylene diisocyanates and the arylene diisocyanates), as well as known triisocyanates and polymethylene poly(phenylene isocyanates). Illustrative polyisocyanates are: PA0 higher polymer content, greater than 30 weight percent and up to about 60 weight percent, PA0 lower viscosities, typically less than about 20,000 cSt, preferably less than about 15,000 cSt, most preferably below 10,000 cSt, PA0 excellent product stability such that 100% passes through a 150 mesh screen, PA0 exceptionally high amounts of the high polymer content polymer/polyol, up to 100% thereof, pass through a 700 mesh screen test, PA0 a composition for forming high potency preformed stabilizer. PA0 the novel process for making high potency preformed stabilizer; PA0 the high potency preformed stabilizer; PA0 a novel composition for making an enhanced polymer/polyol composition; PA0 a novel process for making polymer/polyols; PA0 a novel polymer/polyol composition; and PA0 unique polyurethanes having high modulus or load-bearing capacity. PA0 (A) a precursor to the stabilizer [designated as precursor (I) herein] comprising an esterified product of reaction of: PA0 (1) providing a heterogenous mixture of the high potency preformed stabilizer (II) and, optionally, liquid diluent (D) above, in combination with PA0 (2) in a reaction zone maintained at a temperature sufficient to initiate a free radical reaction, and under sufficient pressure to maintain only liquid phases in the reaction zone, for a period of time sufficient to react at least a major portion of (b) to form a heterogenous mixture containing the enhanced polymer polyol, unreacted monomers and diluent, and
__________________________________________________________________________ 2,4'-diisocyanatotoluene 2,6-diisocyanatotoluene methylene bis(4-cyclohexyl isocyanate) 1,2-diisocyanatoethane 1,3-diisocyanatopropane 1,2-diisocyanatopropane 1,4-diisocyanatobutane 1,5-diisocyanatopentane 1,6-diisocyanatohexane bis(3-isocyanatopropyl)ether bis(3-isocyanatopropyl) sulfide 1,7-diisocyanatoheptane 1,5-diisocyanato-2,2-dimethylpentane 1,6-diisocyanato-3-methoxyhexane 1,8-diisocyanatooctane 1,5-diisocyanato-2,2,4-trimethypentane 1,9-diisocyanatononane 1,10-disocyanatopropyl)ether of 1,4-butylene glycol 1,11-diisocyanatoundecane 1,12-diisocyanatododecane bis(isocyanatohexyl) sulfide 1,4-diisocyanatobenzene 2,4-diisocyanatotolylene 2,6-diisocyanatotolylene 1,3-diisocyanato-o-xylene 1,3-diisocyanato-m-xylene 1,3-diisocyanato-p-xylene 2,4-diisocyanato-1-chlorobenzene 2,4-diisocyanato-1-nitrobenzene 2,5-diisocyanato-1-nitrobenzene 4,4-diphenylmethylene diisocyanate 3,3-diphenyl-methylene diisocyanate polymethylene poly(phenyleneisocyanates) and mixtures thereof. __________________________________________________________________________
The preferred polyisocyanates are a mixture of 80% 2,4-tolylene diisocyanate and 20% 2,6-tolylene diisocyanate and polymethylene poly (phenyleneisocyanates).